This application claims priority of International application number PCT/DE00/01810, filed May 31, 2000, which in turn claims priority to German patent application number 199 27 033.3, filed Jun. 4, 1999.
The invention relates to a drive acting on both sides for adjustment devices. The invention is intended in particular for the adjustment of vehicle seat components such as seat backs and seat cushions.
From DE 195 27 912 A1 a drive acting on both sides is known where a drive lever is mounted on a drive axle and supports swivel coupling elements whose free ends provided with toothed elements can be brought into engagement with the teeth mounted around the circumference of a drive wheel. The swivel coupling elements are associated with a sliding block guide which lifts the relevant unloaded coupling element from the gearing of the drive wheel according to the swivel direction of the drive lever. Spring areas are thereby provided on both sides and outside of the sliding block guide to exert on the coupling elements a force directed against the engagement direction of the teeth so as to prevent any so-called ratchet or rattling noises.
The drawback with the adjustment drive known from DE 195 27 912 A1 is in the first place the relatively large number of parts. In particular two independent coupling elements are required for an adjustment on both sides; this is linked with a correspondingly large structural space taken up by the adjustment drive. Secondly an expensive construction is required in order to guide the coupling elements in a defined manner and to prevent the teeth of the coupling elements from catching on the teeth of the drive wheel when the drive lever is returned to the zero point position.
Starting from the prior art the object of the invention is to provide a drive acting on both sides which produces a rotary movement, which uses a small number of individual parts, is simple to assemble and is characterised by a compact construction. The drive during use should operate substantially free of play and produce no switching or rattling noises.
The solution according to the invention proposes that the coupling element is mounted for both radial displacement and tilting movement in a guide whereby the two coupling areas are coupled spring-elastically to the drive wheel when the drive lever is in the zero point position. When the drive lever is moved out of the zero point position the non-loaded coupling area is uncoupled from the drive wheel through the sliding block guide and remains uncoupled when the drive lever is moved in the opposite direction, thus moved towards the zero point position.
Although play is required owing to the one-piece design of the coupling element, the drive appears subjectively free of play since the actual idling path which has to be covered up to rotation of the drive wheel is loaded through the spring-elastic pretension. This pretension can be produced for example by a coil spring which is supported on one side radially on the drive lever and on the other side on the coupling element, whereby the coupling area is pressed into the associated coupling area of the drive wheel. By way of example a coil spring presses the coupling element against the drive wheel whereby the movement of the drive lever overall is found to be free of play. Furthermore with the solution according to the invention no engagement click occurs since the coupling element is brought smoothly through the resilient tension into an entrainment position and not merely by applying a drive force.
In order to ensure a secure accurate guide of the coupling element in the radial direction a guide element is provided which is connected to the coupling element and which engages in a recess of the drive lever. This recess thereby extends in the radial direction and is formed for example as an oblong hole.
In an alternative embodiment the guide element is mounted on the drive lever and the radial recess which acts as a type of slide guide is worked into the coupling element. The guide element can be connected in one assembly process, for example by welding, riveting or screwing, to the drive lever or to the coupling element or can be formed by pressing or drawing. The recess is normally punched out. Similarly, the formation of the recess is possible in a re-shaping process.
Under certain circumstances it can be favourable in order to guarantee a uniform substantially non-jerky movement of the guide element to provide a slide block which connects the guide element to the radial recess. Through the slide block it is possible to produce a favourable friction pairing irrespective of the material of the guide element and of the component part enclosing the recess.
This recess is preferably dimensioned so that with maximum displacement of the coupling element towards the drive axle both coupling areas are not exactly coupled to the drive wheel. It is thereby reached that the play of the adjustment drive is minimal.
According to the invention a spring is mounted between a housing of the adjustment drive and the coupling element wherein the spring biases the coupling element radially in the direction of the drive wheel so that the two coupling areas in the zero point position of the drive lever reliably adjoin the drive wheel.
In one embodiment of the invention a spring is provided between the drive lever and the coupling element whereby it is favourable if the spring is mounted between the drive lever and a guide element of the coupling element.
In order to ensure a definite engagement of the coupling areas with the drive wheel it is advantageous to provide a keyed connection to transfer the force applied through the drive lever. To this end both the coupling areas of the coupling element and the circumference of the drive wheel are provided with teeth which are associated with each other so that the two toothed areas can engage in each other. The teeth of the drive wheel can thereby be formed as internal or external teeth.
Since the manufacture of the teeth, particularly internal teeth, is time-consuming and expensive, as an alternative to the keyed connection the coupling area is coupled in friction engagement with the drive wheel. The coupling areas of the coupling element and the circumference of the drive wheel are thereby designed accordingly, for example by coating with a friction lining so that the transfer of the required torque between the coupling element and drive wheel takes place through friction engagement.
The sliding block guide for controlling the coupling element is formed in one embodiment of the invention in a cover element of the drive.
In one development of the invention resilient elements are provided on both sides outside of the guide areas of the slide block and during movement of the drive lever towards the zero point position cause the coupling area which was previously loaded, to be lifted from the drive wheel. The spring force is thereby designed so that when the drive lever is moved out of the zero point position it allows the coupling areas to adjoin the drive wheel and at the same time guarantees that the coupling element is lifted when no force is introduced through the drive lever for adjusting the seat back for example.
For this, guide elements are arranged on the coupling element in the form of pins for example which are guided in the sliding block guide and which are in contact outside of the sliding block guide areas with resilient areas in order to engender the lifting movement of the coupling element in the absence of drive force so that no rattling or ratchet noises occur during the resetting movement. In a further development of the invention the guide elements have a non-rounded corner section so that during movement of the coupling element over the zero point position the reversing play is minimised.
A further development of the solution according to the invention is characterised in that a secondary force is exerted on the coupling element during an adjustment process such that when the drive lever is moved out of the zero point position torque is produced on the loaded coupling area in the direction of the drive wheel and when the drive lever is moved towards the zero point position torque is produced in the direction of lifting the loaded coupling area away from the drive wheel.
With this development of the solution according to the invention a more cost-effective play-free drive is provided which causes on one side a fixed coupling between the coupling area of the coupling element which is active in the relevant adjusting direction, and the drive wheel when the drive lever is moved out from the zero point position and on the other hand ensures a silent resetting of the drive lever back into the zero point position.
An advantageous development of this solution according to the invention for a drive where the coupling areas of the coupling element are formed as teeth, and toothing is provided on the circumference of the drive wheel associated with the teeth, is characterised in that when the drive lever is moved out from the zero point position torque is produced on the loaded coupling area in the sense of a toothed engagement and when the drive lever is moved in the direction of the zero point position torque is produced in the sense of separating the toothed engagement.
With this design of the invention on the one hand there is a fixed toothed engagement between the teeth of the coupling area of the coupling element which is active in the relevant adjusting direction and of the drive wheel when the drive lever is moved out from the zero point position and on the other it is guaranteed that the drive lever is reset into the zero point position without any ratchet noises.
A secondary force acts on the coupling element during an adjusting process to produce a torque in the direction of a reinforced coupling of the loaded coupling area and drive wheel when the drive lever is moved out of the zero point position. Likewise, a secondary force produces a torque in the direction of lifting the loaded coupling area from the drive wheel during movement of the drive lever in the direction of the zero point position. This secondary force is preferably achieved through axial tensioning of the coupling element, preferably outside of the zero point position of the drive lever.
This design ensures, in addition to a quasi play-free drive, a fixed coupling between the coupling element and drive wheel as well as the elimination of ratchet noises, that the coupling element in the zero point position is coupled with the drive wheel through the action of the spring acting on the coupling element and that the coupling element is fixed and thus no rattling or ratchet noises can occur.
Producing the axial tensioning of the coupling element is preferably carried out through at least one axially acting friction element which is mounted on the coupling element underneath the active line of the rotary point of the coupling element with the connection of the coupling areas to the drive wheel, is supported on a locally fixed part of the drive and in the zero point position of the drive lever is inactive so that the coupling areas are coupled to the drive wheel through the spring elastic connection of the coupling element with the drive lever.
Optionally two friction elements can be mounted on the coupling element one either side next to the drive lever and/or one friction element can be mounted centrally on the coupling element which engages through an opening in the drive lever.
The or each friction element is preferably formed as a leaf spring.